There was a time when users had to write down their Activation keys just in case they lose it someday and need to reinstall Windows – as you can imagine, this was a headache, but it was how things went before Windows 10 showed up.

With Windows 10 Microsoft changed the whole activation process – in an attempt to simplify it and remove the whole DVD-key thing that is frankly getting too old in this age of instant-everything delivered by the Internet.

Microsoft is continuously innovating on the Windows platform – no matter how many fancy features Apple comes up with for OS X, Windows remains the most stable and flexible operating system with a company that provides continuous support backing it.

But no software is perfect – nobody makes bug free software since all code is written by humans and humans make mistakes.

Windows is no exception, so sometimes the activation simply fails and leaves you with no clues about how to fix it. This guide will try and help you figure out what exactly is wrong with your Windows and attempt to fix it.

How do I fix an Activation key that doesn’t work on Windows 10?

Activating Windows 10 isn’t always simple, and issues with the activation key can occur once in a while. Regarding issues, here are some common problems reported by users:

Windows 10 not activated after upgrade

This is a common problem that can occur with Windows 10.

If you encounter it, be sure to try to activate your copy of Windows 10 again.

Windows 10 product key doesn’t work

Sometimes your product key won’t work on Windows 10. If this happens, make sure that your activation key is genuine.

In addition, be sure that this key wasn’t used to activate Windows 10 on other PCs.

Windows 10 activation error 0x803f7001, 0x8007007b

Various errors can occur while trying to activate Windows 10, and if you encounter some of these issues, try to fix them using one of our solutions.

1. Check if Windows is activated

Open the Start Menu and type Activation then click on the See if Windows is activated in results.

Here, if the activation status says Connect to the Internet to activate Windows you can click Activate to manually activate Windows – this will obviously require an internet connection.

This should attempt to reactivate Windows if you are connected to the Internet – this would usually fix all of the problems related to activation for you, but if for some reason this did not work you can give a shot to the 2nd solution.

2. Run SLUI 4 command

Open the Start Menu and type Run, then open the first result.

In the Run prompt, type SLUI 4 and press Enter.

An activation prompt to take over your PC – here you have to select your country and click Next.

Once you have selected your country, you simply have to call one of the listed numbers and follow the instructions given by Microsoft Support.

While the first solution should fix most activation issues as it is quite literally remaking an attempt to activate itself, the 2nd solution will fix your activation issue if there is something wrong with your PC’s settings or activation code.

3. Select Do this later option

If your activation key isn’t working, you might want to try activating Windows 10 later. Due to a large number of users, it’s possible that Microsoft’s servers are overwhelmed and that can cause the problem with activation.

Unfortunately, there’s no way to fix this problem on your own, and you’ll just have to try again in a couple of hours or days. Few users reported that they choose Do this later option, and then their Windows 10 activated a couple of days later automatically, so you might want to consider doing that as well.

4. Restart your Internet connection and your PC

If your activation key isn’t working for Windows 10, the issue might be related to your Internet connections. Sometimes there might be a glitch with your network or its settings, and that can prevent you from activating Windows.

However, you might be able to fix the problem simply by restarting your router/modem. To do that, turn off your router/modem by pressing the power button on it. Wait for 30 seconds and turn the device back on again.

Once your modem/router boots, try to activate the Windows again. If the problem is still there, restart your PC and try again.

In some rare cases, there might a glitch with your system that is interfering with the activation. If that’s so, simply restart your PC and try to activate Windows 10 again.

5. Make sure that you’re trying to activate the correct version

According to users, sometimes your activation key might not work if you’re trying to activate the wrong version of Windows 10. As you know, there are two versions of Windows 10 available, Home and Pro, and the two offer different features.

As a result, the key for Windows 10 Home won’t work for Windows 10 Pro and vice versa. So if you’re unable to activate your copy of Windows 10, be sure that you’re using the activation key for the proper version of Windows.

6. Reset your license status

Enter the following command slmgr.vbs -rearm and press Enter to run it.

In some cases, you might encounter certain glitches while trying to activate Windows 10. If your activation key isn’t working, you might be able to fix the problem by resetting the license status.

After running the command, close Command Prompt and restart your PC. Once your PC restarts, try to activate Windows again.

7. Try to force the activation

Start Command Prompt as administrator like we showed you in one of our previous solutions.

Now enter slmgr.vbs -ato command and press Enter to run it.

After the command is executed, the issue with activation should be resolved.

8. Activate Windows using Command Prompt

Start Command Prompt as administrator.

When Command Prompt starts, enter slmgr.vbs -ipk xxxx-xxxx-xxxx-xxxx and press Enter to run the command. Be sure to replace X letters with the actual activation key.

According to users, you might be able to activate Windows 10 right from Command Prompt. This is relatively simple to do, and you can do it by running a single command. After running this command, the problem should be resolved.

9. Make sure that you use this key on only one PC

If your activation key isn’t working, it’s possible that you already used it to activate another copy of Windows 10 on a different PC. If that’s the case, you’ll need to deactivate the other copy of Windows and then try to activate Windows 10 on your PC.

Keep in mind that your key is tied to the hardware on which it was activated. Even if you don’t use Windows 10 on that old PC, you need to remove license information from the hardware.

If you don’t know how to do that, contact Microsoft and ask them to do that remotely for you.

10. Make sure that your activation key is genuine

On some rare occasions, it’s possible that you can’t activate your copy of Windows 10 because the key isn’t genuine. If you already used this key to activate Windows 10 before, then your key should be genuine and the problem is caused by something else.

However, if this is the first time that you’re trying to activate Windows 10 with this key, it’s possible that the key isn’t genuine. Many third-party websites offer to sell Windows 10 keys, and most of these websites are designed as a scam.

If you want to be sure that your key is 100% genuine, purchase it directly from Microsoft or from one of its official distributors.

FAQ: Learn more about Windows 10 license keys

Do I need an activation key in order to run Windows 10?

Yes. You can run the Windows 10 OS without any functional limitations if you don’t activate your license key.

How do I make sure my WIndows 10 key is genuine?

Third-party websites have been known to offer genuine Windows 10 license key, but the only way you can get a license key and be 100% sure is legitimate is by getting it from the official Microsoft stores.

Can I upgrade to Windows 10 without a license key?

Yes. By using the Installation ISO provided by Microsoft and by following certain steps, you should be able to upgrade from Windows 7, 8 or 8.1 to 10 without any issues.

Windows is an incredible operating system with complexities beyond one person’s understanding, but it is well understood and is able to use by millions around the world because of it.

Licensing and activation problems are something we will have to deal with for as long as Windows costs money.

However, troubleshooting problems related to it have only been getting easier with every iteration, and simply calling Microsoft Support is quite possibly the easiest solution to it.

Editor’s Note:This post was originally published in July 2018 and has been since revamped and updated in March 2020 for freshness, accuracy, and comprehensiveness.